Java设计模式学习之组合模式

组合模式是结构型模式中的一种，他通常可以用来实现类似树结构的功能。

就比如一副画，画由矩形，三角形组成，其中各个形状的颜色不同。这里画就好比跟节点(Tree Root), 各个形状就好比 Tree Leaf，而这些形状就是组成画的基本元素

通过上述比喻，不难推断出组合模式有以下对象组成

  1. Base Component 组合模式中所有对象需要实现的接口类
  2. Leaf 实现Base Component的类，且各个Leaf是互不相关的
  3. Composite 包含Leaf，同时也实现了Base Component

下面我们通过画画这个例子来实现组合模式

Base Component

接口类，提供颜色来表明Leaf 的颜色

Shape.java

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package com.walterlife.dp.CompositeDP;

public interface Shape {
    public void draw(String color);
    public String getName();
}

Leaf 对象

我们可以根据自己的需要创建不同形状的Leaf

Circle.java

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package com.walterlife.dp.CompositeDP;

import org.apache.log4j.Logger;

public class Circle implements Shape {
    
    private String name;

    private static Logger logger = Logger.getLogger(Circle.class);
    
    public Circle(String name) {
        this.name = name;
    } 

    public void draw(String color) {
        logger.info("Circle draw with Color: " + color);
    }

    public String getName() {
        return name;
    }
}

Triangle.java

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package com.walterlife.dp.CompositeDP;

import org.apache.log4j.Logger;

public class Triangle implements Shape {

    private String name;

    private static Logger logger = Logger.getLogger(Circle.class);

    public Triangle(String name) {
        this.name = name;
    } 

    public void draw(String color) {
        logger.info("Triangle draw with Color: " + color);
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }
}

Composite

该类需包含Leaf Objects，同时我们需要提供方法方便添加/删除Leaf，清除全部也可以提供

Drawing.java

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package com.walterlife.dp.CompositeDP;

import java.util.ArrayList;
import java.util.List;

import org.apache.log4j.Logger;

public class Drawing implements Shape {

    private List<Shape> shapes = new ArrayList<Shape>();
    private String name;

    private static Logger logger = Logger.getLogger(Drawing.class);

    public void draw(String color) {
        for(Shape shape: shapes) {
            shape.draw(color);
        } 
    }

    public Drawing(String name) {
        this.name= name; 
    } 

    public void addShapes(Shape shape) {
        if(shape == null) {
            logger.error("Drawing addShapes: shape is null, not valid!!!");        
        } else if(shapes.contains(shape)) {
            logger.warn("Drawing addShapes: shape " + shape.getName() + " is already existing!!!");        
        } else {
            shapes.add(shape);
        } 
    } 

    public void removeShapes(Shape shape) {
        if(!shapes.remove(shape)) {
            logger.warn("Drawing removeShapes: shape does not exist!!!");        
       } 
    } 

    public void clear() {
        logger.info("Drawing clear: clear all shape!!!");
        shapes.clear();
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }
}

Drawing 类和Leaf Classes 类似，也实现了Shape 类的draw 方法，除了他包含了所有Leaf Objects

测试代码

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public static void testComposite() {
    Drawing drawing = new Drawing("Drawing");

    Shape cir = new Circle("Circle");
    Shape tri1 = new Triangle("Triangle");
    Shape tri2 = new Triangle("Triangle");
    
    drawing.addShapes(cir);
    drawing.addShapes(tri1);
    drawing.addShapes(tri2);

    drawing.draw("RED");

    drawing.clear();

    drawing.addShapes(cir);
    drawing.addShapes(tri1);

    drawing.draw("GREEN");
}

测试结果

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2015-09-06 01:15:02 INFO  com.walterlife.dp.CompositeDP.Circle draw:16 -> Circle draw with Color: RED
2015-09-06 01:15:03 INFO  com.walterlife.dp.CompositeDP.Triangle draw:16 -> Triangle draw with Color: RED
2015-09-06 01:15:03 INFO  com.walterlife.dp.CompositeDP.Triangle draw:16 -> Triangle draw with Color: RED
2015-09-06 01:15:03 INFO  com.walterlife.dp.CompositeDP.Drawing clear:42 -> Drawing clear: clear all shape!!!
2015-09-06 01:15:03 INFO  com.walterlife.dp.CompositeDP.Circle draw:16 -> Circle draw with Color: GREEN
2015-09-06 01:15:03 INFO  com.walterlife.dp.CompositeDP.Triangle draw:16 -> Triangle draw with Color: GREEN

留言

Sep 5 2015
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